Objects of investigation: 1. Steroid metabolism: Further characterization and comparison of the nature and extent of the gastrointestinal, pulmonar and renal metabolism of steroids. Metabolic fate of inhaled steroids (testosterone, beclomethasone dipropionate). Intracellular localization of inhaled steroids by autoradiography. Pulmonal and renal clearance of circulating unconjugated steroids. 2. Toxification-detoxification: The metabolism of xenobiotics in liver and in several extrahepatic organs, which serve as an interface with the environment (e.g., gut, skin). The properties and the effects of hepatic xenobiotic biotransformation modifiers on the soluble enzyme, flutathione S-epoxide transferase and on microsomal epoxide hydrases. The properties of toxification-detoxification enzymes in liver biopsies of man. Further purification of microsomal UDP-glucuronosyltransferase, the reaction kinetics of the purified product. The recombination in vitro of microsomal monooxygenase and purified UDPglucuronosyltransferase. The structural and functional relationship of these enzymes in the endoplasmic reticulum membrane and the localization of UDPglucuronosyltransferase. The xenobiotic detoxification/toxification in acute heavy metal poisoning (lead, methylmercury, cadmium). The protection against toxicity induced by reactive intermediates.